Dr. Chuck Ray, Associate Professor of Wood Operations at Penn State discusses how biomass harvesting and the carbon cycle are often misunderstood.

By Chuck RayDate Posted: 9/1/2012

Misleading information about sustainable forestry, bioenergy and how the carbon cycle works is prevalent in American society.

Information posted earlier this year on the website of the Natural Resource Defense Council (NRDC) is an example of just such information and illustrates clearly the lack of understanding of forest ecosystems and the carbon cycle in general.

A video and its accompanying text on the website decry the use of forest harvesting for biomass energy. However, they admit that “Biomass can be harvested and utilized in ways that reduce pollution and protect forest habitats, but only with sustainability safeguards and proper accounting for carbon emissions – including carbon released due to deforestation.” This definition of sustainable biomass production includes agricultural biomass and woody biomass from short-rotation biomass plantations, but not natural forests.

A “biomass carbon deficit” argument is put forward, along with an overly-simplistic example of one forest harvested, and one left to grow. The claim is that the harvested forest creates an immediate carbon deficit compared to the one that is left, and that the deficit is closed slowly over the years, until eventually, the harvested forest will start producing carbon reductions.

What this comparison fails to take into account is the cumulative effect of multiple forest stand harvesting over continuous time periods. Rather than comparing one forest harvested immediately and one left for fifty years, consider the forest as one comprised of fifty different forest stands harvested one per year, and growing at a rate of 2% each year. This is closer to reality and yields a cumulative impact of a sustainable harvest in perpetuity, with no real starting or ending point to the carbon cycle.

Also consider that each of these stands was collecting carbon from the atmosphere before they ever reached harvesting age. In the example, the stand harvested in Year One had been growing for at least fifty years on the harvest date. It will be ready to be harvested again at the end of another fifty-year cycle. Thus, the “carbon deficit” is only real if you ignore the fact that the trees gobbled up carbon before they were harvested.

Narrow arguments against forest biomass energy such as the NRDC’s also tend to ignore some basic realities of sustainable forestry and markets...

1.) Biomass harvests are rarely, if ever, stand-alone operations. For fundamental economic reasons, forest biomass (which is typically called “pulpwood” in the industry) is harvested as a co-product of sawlog harvesting, either at the same time as the sawlog harvest or prior to the sawlog harvest as a thinning treatment. Natural forests will not be treated merely as “fuel depots” within the construct of sustainable forest management; all the other products of the forest, including lumber, air and water quality, wildlife habitat, and recreation are optimized to meet the management objectives of the land owner.

2.) Any biomass energy industry that develops here in North America is able to do so only because the pulp industry here has been on the decline for the past two decades. Pulpwood harvested for biomass energy is simply filling a vacuum created in the marketplace by the decline of pulp production. And all biomass that was harvested in the past for pulp and paper production ultimately returned to the atmosphere as carbon, either through its use for mill energy in the form of black liquor, or as waste paper that ended up in landfills.

3.) As pulpwood markets have shrunk, large portions of the northeastern, Great Lakes, and western forests have become overburdened with small-diameter stems that are densely-packed and growing far more slowly than the healthier forests of previous decades when an appropriate pulpwood component was being harvested. Dense, slower growing forests mean less carbon sequestration per acre and more hazard of wildfire, both situations that can be reversed by increased levels of biomass harvesting.

4.) This harvesting of the pulpwood component is an essential part of forest health and restoration. The growing bioenergy industry provides a way to pay for this benefit to the forest. Without it, the balance of forest ecosystems will come under even more pressure as “sawlog only” harvests become ever more prevalent.

5.) Biomass energy production will always be driven, and limited, by the marketplace. As more facilities are built, local market prices for the biomass will rise and biomass energy operations will be harder to justify economically. Fears that biomass harvesting will wipe out the forest are overblown, as even today the market works as a natural constraint against a broad expansion of biomass energy facilities.

6.) Biomass energy production is an enabling technology for more advanced bio-refinery processes and products. Bioenergy-related companies seeking to add value to the biomass raw material will be the ones that bring us advances in cellulose and lignin utilization, and produce the miracle bio-products of tomorrow, including those that replace products of fossil fuels. Without biomass energy providing the economic incentive to resurrect the pulpwood harvesting industry, these future miracle bio-products will never see the light of day.

7.) All other forms of energy production, including the solar, wind, and agricultural biomass touted on the NRDC videos, also have environmental and societal drawbacks to some extent. Can we say which is better or worse? In general, the answer is “No.” But in specific applications, experts usually can identify a best choice. And sometimes biomass energy from natural forests is the best option.

The NRDC videos do make valid points about relative efficiency of wood versus fossil fuel energy production. It’s lower, and this does result in relatively more emissions per unit of energy, at a higher cost in large-scale applications. That’s the reasoning that went into our discussion of using biomass energy in appropriate applications, or as we put it, “Size Matters” when determining the best use of biomass for energy applications. But by presenting biomass energy production as a “one size fits all” proposition, opponents of natural forest biomass energy like the NRDC are able to misrepresent the resource potential and mislead the public into thinking that harvesting the forest for biomass is a bad thing in general.

While some studies theorize that certain scenarios of biomass-to-energy harvesting and conversion may in fact increase overall carbon emissions, the science is ongoing and government-funded research tends to focus on large-scale processing. This is a practice that many in the industry believe is a sub-optimal use of the forest resource compared to right-sized biomass harvesting that can improve the overall ecosystem quality of the forest.

A video produced by the National Geographic Society demonstrates modern understanding of and technology utilization in sustainable forestry, and features some forest products industry companies in Pennsylvania.

By following sustainable harvest guidelines, society will benefit from the capture of woody conversion of carbon stock to energy in our homes and businesses. Ultimately, if we don’t, the carbon is returned back to the atmosphere anyway, one way or another.

Would you prefer that forest biomass and its carbon molecules heat your home or local business, or heat the atmosphere out in the woods? Ultimately, it’s one or the other. No forest lives forever. It’s continually dying, being reborn, growing, aging and dying again. Those who think they are “defending” the forest seem to be instinctively against human management and utilization of natural resources, despite the fact that forests in most areas of the world that have been responsibly managed for the last fifty years are larger and healthier now than they’ve been in centuries. They imagine that we’ll all be better off if we just leave the forest alone and use other resources they deem to be more environmentally-friendly.

In fact, the use of misleading “carbon deficit” accounting just seems to be the latest angle at stopping forest harvesting, period. Just like “clearcutting” in the 1980’s and “endangered species” in the 90’s, “carbon deficits” is the cause célèbre for those who would like to see a day when no forest tree is ever cut down. But this too will pass, and in the end, we’ll benefit from the knowledge gained by further, more balanced research into the workings of forest ecosystems and the carbon cycle.